Difference Between Should and Must

The words “should” and “must” are modal auxiliary verbs or simply modals. They provide information about the function of the main verb following it. Both “should” and “must” are similar in meaning except that “must” is a much stronger word as compared to “should.”

“Should” is the past tense of “shall.” “Should” is used to denote recommendations, advice, or to talk about what is generally right or wrong within the permissible limits of society. For instance:

In all these statements, there is a probability or recommendation of some kind.

“Must” is used to talk about an obligation or a necessity. It is used when people are compelled to do something. For instance:

You must clean the house as your mom is not well.

Here, it is imperative that you clean the house or else the house won’t be cleaned and remain untidy.

We must obey the law.

This statement compels us to abide by the law or we will have to face the punishment enforced by the law.

You must hurry if you have to catch the train.

In this statement, it is emphasized that you certainly have to move quickly as you are running late. If you do not hurry up, you will miss the train. This sentence is an example of a compellation for achieving a certain aim.

One must keep his word.

Here again the sentence directs that people are required to or are compelled to do something (here it is keeping one’s word) by the use of threat or force.

The main difference between the two words “should” and “must” is that “must” is a stronger word, as mentioned before. The probability of “must” is much more than that of “should.” For instance:

You must do your homework now. (It is already late, and if you do not start doing your work now, you will not be able to finish your work on time. This will lead to punishment or a penalty.)

You should do your homework now. (It is the right time that you start doing your work.)

You must rest. (You are not well, and if you continue working, your health is going to get worse.)

You should take a rest. (You are tired, and if you do not take a rest, you are going to get sick.)